The present invention relates to non-destructive inspection (NDI) instruments, and more particularly to a peak visualization enhancement display system for said instruments which replicates the so-called haloing effect of analog cathode ray tube (CRT) displays.
Any discussion of the related art throughout this specification should in no way be considered as an admission that such art is widely known or forms a part of the common general knowledge in the field.
As digital signal processing methods and techniques have increased in power, speed, and availability in recent years, portable electronic systems which digitize and process data in real time have increased in popularity. This is especially true of the NDI industry. Many of the functions once handled by bulky, complex, and in some cases costly analog circuits are now performed completely, and in many cases more efficiently, within digital electronics such as digital signal processors or custom designed FPGAs. Such functions include, but are not limited to, filtering to shape and improve the quality of test waveforms, applying complex time varied gain curves to facilitate real time analysis of data, and automated analysis of test data. The advanced functions within NDI instrumentation provided by digital signal processing methods and techniques offer a practically countless array of improvements and benefits over more traditional analog systems.
One such improvement offered by digital systems is in waveform display. Digital systems can readily (in real time or within an acquire/playback architecture) compress large amounts of digital waveform data and plot it on a high resolution digital display module, such as an LCD or VGA display. In recent years such displays have reduced in cost and power consumption while offering an ever increasing image quality. Such displays have become ideal for use within NDI instrumentation, which typically requires that a detailed digitized waveform be displayed for an end user in real time and with a high frame rate—that is, the rate at which the waveform data is updated and refreshed.
While digital waveform displays, making use of intelligently compressed waveform data displayed at high resolution, offer significant improvements over prior art analog CRT displays, one aspect of analog CRT systems is lost in the move to digital display systems.
CRT display systems function by directing an electron beam, sometimes referred to as a cathode ray, through a vacuum tube and onto a phosphorus coated screen. This causes the phosphorus on the areas of the screen impacted by the electron beam to light up briefly. By directing the electron beam to move across the screen in a particular pattern, an image can be formed on the screen. In analog CRT waveform displays, as are common in older analog NDI instrument designs, this technique can be used to quite effectively draw an image of a waveform on a display screen.
One aspect of an analog CRT display system is the so-called haloing effect. As the electron beam moves horizontally across the phosphorus coated screen at a constant speed, it shifts vertically up and down to trace the desired waveform. At those points where the slope of the waveform is zero—that is, at those points where the electron beam switches from moving vertically up to vertically down or vise versa—the electron beam will pause briefly. This has the effect of hitting the phosphorus on the screen at these zero slope points with more electrons than other parts of the waveform. As a result, these zero slope points will tend to glow brighter than the rest of the waveform, haloing the peaks and valleys of the waveform.
This haloing effect is simply a side effect characteristic of the analog CRT display system. As the electron beam sweeps across the phosphorus coated screen to trace a waveform, its vertical velocity pauses (becomes zero) for a brief time at each zero slope point. This characteristic has become a useful feature within analog CRT display systems, in particular with analog NDI instruments. The haloing effect allows an end user to readily observe waveform peaks that would otherwise be lost within larger peaks. This is especially true of situations in which an NDI instrument is displaying a large range of data—that is, when the display is showing a very long waveform. In such cases, waveform peaks, which are of great interest to the inspection operation, are drawn very close together and often appear muddled together, indistinguishable from each other aside from the haloing effect.
As such, the haloing effect of analog CRT display systems has become an invaluable tool to a certain subset of very highly skilled NDI operators. Operators performing ultrasonic flaw detection inspections on nuclear vessel walls (the very thick walls used to shield nuclear reactors), for example, rely on the CRT haloing effect to observe flaws near or within the large backwall echo inherent to such an inspection. Similarly, operators performing intergranular stress corrosion cracking (IGSCC) inspections often encounter complex, so-called spindle cracks which propagate in multiple directions along the grain of a course material. The ultrasonic reflections from the multiple facets of spindle cracks have a tendency to conflate together, returning a tightly packed, irregular echo with multiple peaks. Taking advantage of the haloing effect, however, a skilled operator can accurately locate and size such a complex crack in a material under inspection.
As the haloing effect does not exist in digital displays, many operators who rely on it are reluctant or unable to use the more advanced NDI instruments offered in the marketplace today. This prevents such operators from benefiting from the many advantages of digital NDI systems and limits the effectiveness and accuracy of their inspection operations. Some attempts have been made to mimic the haloing effect in digital NDI instruments (most notably the so-called “Sparkle” feature offered in some portable instruments offered by GE Inspection Technologies, located in Billerica, Mass.) by simply highlighting the maximum value of each compression zone, but this technique is lacking. It does not accurately represent peak values in highly compressed data, and it does not preserve peak information when multiple peaks are displayed in very close vicinity on a display.
Accordingly, it would be advantageous to provide a digital display system that replicated the haloing effect of analog CRT display systems. Further it would be advantageous if this digital display system accurately displayed peak values within highly compressed data. It would also be advantageous if this digital display system preserved all peak information, regardless of range and compression ratio settings. It would further be advantageous if the display system offered controls or measures to prevent the detection and display of so-called false peaks caused by noise spikes and the like within the waveform without sacrificing any resolution in the digitized waveform.